pydoc > _signal

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📋 NAME

_signal - This module provides mechanisms to use signal handlers in Python.

🚀 Quick Reference

🎯 Use Case	⚙️ Command	📝 Description
Set a signal handler	signal(signalnum, handler)	Set the action for a given signal
Get current handler	getsignal(signalnum)	Return the current action for the given signal
Alarm after delay	alarm(seconds)	Cause SIGALRM after specified time (Unix only)
Wait for signal	pause()	Wait until a signal arrives (Unix only)
Set interval timer	setitimer(which, seconds, interval)	Set an itimer with initial and interval time
Send signal to thread	pthread_kill(thread_id, signalnum)	Send a signal to a thread
Block/unblock signals	pthread_sigmask(how, mask)	Fetch/change signal mask of calling thread
Wakeup fd on signal	set_wakeup_fd(fd)	Set fd to be written when signal arrives

📖 DESCRIPTION

Functions:

• alarm() -- cause SIGALRM after a specified time [Unix only]
• setitimer() -- cause a signal (described below) after a specified float time and the timer may restart then [Unix only]
• getitimer() -- get current value of timer [Unix only]
• signal() -- set the action for a given signal
• getsignal() -- get the signal action for a given signal
• pause() -- wait until a signal arrives [Unix only]
• default_int_handler() -- default SIGINT handler

signal constants:

• SIG_DFL -- used to refer to the system default handler
• SIG_IGN -- used to ignore the signal
• NSIG -- number of defined signals
• SIGINT, SIGTERM, etc. -- signal numbers

itimer constants:

• ITIMER_REAL -- decrements in real time, and delivers SIGALRM upon expiration
• ITIMER_VIRTUAL -- decrements only when the process is executing, and delivers SIGVTALRM upon expiration
• ITIMER_PROF -- decrements both when the process is executing and when the system is executing on behalf of the process. Coupled with ITIMER_VIRTUAL, this timer is usually used to profile the time spent by the application in user and kernel space. SIGPROF is delivered upon expiration.

*** IMPORTANT NOTICE ***
A signal handler function is called with two arguments: the first is the signal number, the second is the interrupted stack frame.

🔧 FUNCTIONS

• alarm(seconds, /) — Arrange for SIGALRM to arrive after the given number of seconds.
• default_int_handler(signalnum, frame, /) — The default handler for SIGINT installed by Python. It raises KeyboardInterrupt.
• getitimer(which, /) — Returns current value of given itimer.
• getsignal(signalnum, /) — Return the current action for the given signal. The return value can be: SIG_IGN if the signal is being ignored, SIG_DFL if the default action is in effect, None if an unknown handler is in effect, anything else the callable Python object used as a handler.
• pause() — Wait until a signal arrives.
• pidfd_send_signal(pidfd, signalnum, siginfo=None, flags=0, /) — Send a signal to a process referred to by a pid file descriptor.
• pthread_kill(thread_id, signalnum, /) — Send a signal to a thread.
• pthread_sigmask(how, mask, /) — Fetch and/or change the signal mask of the calling thread.
• raise_signal(signalnum, /) — Send a signal to the executing process.
• set_wakeup_fd(fd, *, warn_on_full_buffer=True) -> fd — Sets the fd to be written to (with the signal number) when a signal comes in. A library can use this to wakeup select or poll. The previous fd or -1 is returned. The fd must be non-blocking.
• setitimer(which, seconds, interval=0.0, /) — Sets given itimer (one of ITIMER_REAL, ITIMER_VIRTUAL or ITIMER_PROF). The timer will fire after value seconds and after that every interval seconds. The itimer can be cleared by setting seconds to zero. Returns old values as a tuple: (delay, interval).
• siginterrupt(signalnum, flag, /) — Change system call restart behaviour. If flag is False, system calls will be restarted when interrupted by signal sig, else system calls will be interrupted.
• signal(signalnum, handler, /) — Set the action for the given signal. The action can be SIG_DFL, SIG_IGN, or a callable Python object. The previous action is returned. See getsignal() for possible return values. *** IMPORTANT NOTICE *** A signal handler function is called with two arguments: the first is the signal number, the second is the interrupted stack frame.
• sigpending() — Examine pending signals. Returns a set of signal numbers that are pending for delivery to the calling thread.
• sigtimedwait(sigset, timeout, /) — Like sigwaitinfo(), but with a timeout. The timeout is specified in seconds, with floating point numbers allowed.
• sigwait(sigset, /) — Wait for a signal. Suspend execution of the calling thread until the delivery of one of the signals specified in the signal set sigset. The function accepts the signal and returns the signal number.
• sigwaitinfo(sigset, /) — Wait synchronously until one of the signals in *sigset* is delivered. Returns a struct_siginfo containing information about the signal.
• strsignal(signalnum, /) — Return the system description of the given signal. The return values can be such as "Interrupt", "Segmentation fault", etc. Returns None if the signal is not recognized.
• valid_signals() — Return a set of valid signal numbers on this platform. The signal numbers returned by this function can be safely passed to functions like pthread_sigmask.

📊 DATA

• ITIMER_PROF = 2
• ITIMER_REAL = 0
• ITIMER_VIRTUAL = 1
• NSIG = 65
• SIGABRT = 6
• SIGALRM = 14
• SIGBUS = 7
• SIGCHLD = 17
• SIGCLD = 17
• SIGCONT = 18
• SIGFPE = 8
• SIGHUP = 1
• SIGILL = 4
• SIGINT = 2
• SIGIO = 29
• SIGIOT = 6
• SIGKILL = 9
• SIGPIPE = 13
• SIGPOLL = 29
• SIGPROF = 27
• SIGPWR = 30
• SIGQUIT = 3
• SIGRTMAX = 64
• SIGRTMIN = 34
• SIGSEGV = 11
• SIGSTOP = 19
• SIGSYS = 31
• SIGTERM = 15
• SIGTRAP = 5
• SIGTSTP = 20
• SIGTTIN = 21
• SIGTTOU = 22
• SIGURG = 23
• SIGUSR1 = 10
• SIGUSR2 = 12
• SIGVTALRM = 26
• SIGWINCH = 28
• SIGXCPU = 24
• SIGXFSZ = 25
• SIG_BLOCK = 0
• SIG_DFL = 0
• SIG_IGN = 1
• SIG_SETMASK = 2
• SIG_UNBLOCK = 1

📁 FILE

(built-in)

📋 NAME 🚀 Quick Reference 📖 DESCRIPTION 🔧 FUNCTIONS 📊 DATA 📁 FILE